C2: Reactions- Key Concepts

Question 1

nucleophiles are ____ and want a ____ charge

Answer 1

electron rich; positive

Question 2

the requirements for a nucleophile are:
- to have a ____ charge OR a ____ charge
- a ___ OR ____ bond electrons

Answer 2

• full negative; partial negative
• lone electron pair; pi

Question 3

nucleophiles ____ a pair of electrons and form a ____ bond. they are lewis ____

Answer 3

donate; covalent; bases

Question 4

when comparing the same atom, a more ___ charge makes a stronger nucleophile

Answer 4

negative

Question 5

for atoms in the same period on the periodic table, nucleophilicity ____ as electronegativity decreases

Answer 5

increases

Question 6

when comparing atoms in the same family, nucleophilicity ____ as size increases

Answer 6

increases

Question 7

electrophiles are electron ____

Answer 7

deficient

Question 8

electrophiles have a full ____ charge OR a partial _____ charge

Answer 8

positive; positive

Question 9

electrophiles ____ a pair of electrons and acquire a ____ bond. they are lewis ____

Answer 9

accept; covalent; acids

Question 10

good leaving groups have a ____ C-LG bond to start, are ____ and are electron ____ groups. they are also stable and unreactive once gone and ____ or very ____ bases, are stabilized via ____, and are large and can polarize ____ charge.

Answer 10

weak; electronegative; withdrawing; neutral; weak; resonance; negative

Question 11

a bad leaving group is a ____ base but can be made into a good leaving group via ____

Answer 11

strong; protonation

Question 12

another bad leaving group is ____ but can be made into a good leaving group in 3 ways which are…

Answer 12

hydroxide
- tosylation (OH’s changed to OT’s)
- mesylation (OH’s changed to OM’s)
- switch it to a halide (OH’s are changed to halogens)

Question 13

carbocations are electron ____ (deficient/ rich) and are stabilized by electron ____ (donating/withdrawing) groups

Answer 13

deficient; donating

Question 14

radicals are electron ____ (deficient/ rich) and are stabilized by electron ____ (donating/withdrawing) groups

Answer 14

deficient; donating

Question 15

carbanion are electron ____ (deficient/ rich) and are stabilized by electron ____ (donating/withdrawing) groups

Answer 15

rich; withdrawing

Question 16

stability ____ with carbocations (secondary, tertiary, quaternary). unstable carbocations can undergo ____ to a directly adjacent and ____ order carbon which ____ the stability of the carbocation

Answer 16

increases; rearrangement; higher; increases

Question 17

in order for stability of a carbocation to increase, there are 2 options…
- both of these options have the same conclusion…

Answer 17

1. hydride shift
2. methide shift
   - they can only shift directly to the carbon next door and are shifting to get a higher order (ex: secondary to tertiary)

Question 18

what is a regiospecific rxn?
- selective species are ____ to react and favor more ____ intermediates

Answer 18

a rxn that produces one constitutional isomer and often involves the use of selective species (favor producing stable intermediates)
- slower; stable

Question 19

what is a non-regiospecific rxn?
- reactive species are ____ to react and choose a location where it will ____

Answer 19

a rxn that produces more than one constitutional isomer and often involves the use of reactive species
- faster; react better

Question 20

what does a stereospecific rxn produce?

Answer 20

one stereoisomer that is EITHER:
R or S
cis or trans
E or Z

Question 21

what does a nonstererospecific rxn produce?

Answer 21

more than one stereoisomeric product that is:
R and S
cis and trans
E and Z

Question 22

for SN2 and SN1 reactions, describe the following difference for each:
# of steps
- SN2
- SN1

Answer 22

• 1
• at least 2

Question 23

for SN2 and SN1 reactions, describe the following difference for each:
electrophile
- SN2
- SN1

Answer 23

• smaller is better
• more substituted is better

Question 24

for SN2 and SN1 reactions, describe the following difference for each:
nucleophile
- SN2
- SN1

Answer 24

• strong and small
• weak is ok

Question 25

for SN2 and SN1 reactions, describe the following difference for each:
transition states
- SN2
- SN1

Answer 25

• 1
• at least 2 (1 per step)

Question 26

for SN2 and SN1 reactions, describe the following difference for each:
regioselective
- SN2
- SN1

Answer 26

• yes, backside attack of nucleophile
• no, carbocation rearrangements

Question 27

for SN2 and SN1 reactions, describe the following difference for each:
stereospecific
- SN2
- SN1

Answer 27

• yes, inversion of configuration
• no, racemization

Question 28

for E2 and E1 reactions, describe the following difference for each:
# of steps
- E2
- E1

Answer 28

• 1
• 2

Question 29

for E2 and E1 reactions, describe the following difference for each:
electrophile
- E2
- E1

Answer 29

• more substituted double bonds are more stable
• ” “

Question 30

for E2 and E1 reactions, describe the following difference for each:
base
- E2
- E1

Answer 30

• strong
• weak

Question 31

for E2 and E1 reactions, describe the following difference for each:
transition states
- E2
- E1

Answer 31

• 1
• 2

Question 32

for E2 and E1 reactions, describe the following difference for each:
intermediates
- E2
- E1

Answer 32

• none
• carbocation

Question 33

for E2 and E1 reactions, describe the following difference for each:
product prediction
- E2
- E1

Answer 33

• usually regioselective due to antiperiplanar attack, small base= zaitsev, strong bulky base= hoffman
• usually NOT regioselective due to carbocation rearrangements, zaitsev > hoffman, trans > cis